Grant, in U.S. Pat. No. 3,523,138 granted Aug. 4, 1970, described the treatment of xanthophylls with aqueous alkali materials. The result was said to be an increase in the pigmenting activity. The alkali-treated xanthophyll material was used as such, or dispersed in vegetable oil, or incorporated into a dry product such as, for example, calcium silicate, soybean meal, saturated fat material, gelatin, or starch. The treated xanthophyll, whether in a concentrate, a dispersion, or in a solid product, was then incorporated in poultry feed for increasing pigmentation activity.
A later U.S. Pat. No. 3,535,426 described the technique of mixing an alkali-treated xanthophyll material with a large amount of a fatty acid, which served as a carrier. The very high quantities of fat employed were said to increase the stability of the product.